The three-hour opera, featuring sets and costumes by British fashion designer Zandra Rhodes, was riveting. But it can be a little seat-numbing. So midway through the first act, I removed the thick wallet from my back pocket, placed it on the floor of the center's Brown Theater and settled in for the rest of the performance.

At intermission, I reached down to retrieve the wallet and accidentally pushed it through an air vent in the floor. While it was a stupid thing to do, it helped to discover I'm not alone.

Reda Richardson, the building's event coordinator, says engineers have retrieved cell phones, diamond earrings, necklaces, wallets and loose change that fall through dozens of round floor vents underneath the orchestra level seats. (The vents are capped, but belongings sometimes make their way through side openings.)

The objects fall into a big room known as a plenum. The room, which resembles the underside of stadium bleachers, allows air to circulate through the hall and is accessible by a deep ladder that resembles the entry to the mysterious hatch in the television show Lost.

The plenum is so big that a few years back some workers kept a big bale of hay down there as a target for bow and arrow practice. HGO audio department head Eddie Hawkins says he's dreamed of putting a nap room down there, but too many dust bunnies are floating around.

My day at the opera ended up happier than Aïda's. Just as the second act began, an official came down the aisle with my wallet. This time it went into my back pocket, where it belonged.